A forest quality comprehensive index evaluation method and system

Abstract

The present invention belongs to the field of forest quality evaluation, and discloses a forest quality comprehensive index evaluation method and system, the method comprising: S1, using an improved aerial photography scheme to shoot a forest to be evaluated, and obtaining a plurality of aerial images; S2, obtaining a spliced ​​image based on a plurality of aerial images; S3, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image; S4, calculating the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage. The route planning method of the present invention can avoid setting too small intervals between routes when an area with a high altitude change rate appears, and can effectively reduce the number of routes. In addition, the present invention uses an adaptive shooting interval to shoot on the same route, thereby increasing the number of aerial images of areas with a high altitude change rate, and can also maintain the effectiveness of the spliced ​​images obtained by splicing based on the aerial images obtained by shooting.

Description

Technical Field

[0001] The present invention relates to the field of forest quality evaluation, and in particular to a forest quality comprehensive index evaluation method and system. Background Art

[0002] Forest quality comprehensive index evaluation refers to obtaining scores of multiple aspects of the forest, and then weighting and summing these scores according to the weight of each aspect to finally obtain a comprehensive index of forest quality. The multiple aspects here include vegetation coverage, economic value, control quality, etc.

[0003] In the process of calculating the vegetation coverage rate, it is generally necessary to first obtain aerial images of the forest area to be evaluated, and then identify the aerial images to obtain the vegetation area in the forest area. In the process of serpentine route planning in the forest area, when the altitude change rate of the forest area is greater, the interval between two adjacent routes is usually set smaller, and on each route, the aerial photography position is set at a fixed distance interval. Such a setting can increase the number of aerial images obtained, so as to obtain aerial images of more shooting directions of mountains with larger altitude change rates, effectively reducing the area that cannot be photographed due to the obstruction of the mountain, thereby improving the accuracy of the vegetation coverage rate calculated based on the aerial images. However, when the drone is shooting along the entire route, the route is not entirely made up of mountains with a large altitude change rate. There are also some mountains with a small altitude change rate. If there is only a small section of the route that contains mountains with a large altitude change rate, and the interval between the route and another adjacent route is still set to be relatively small, then too many aerial images will be collected for the mountains with a small altitude change rate. Obviously, this will result in more aerial images requiring more processing time when the vegetation coverage rate is subsequently calculated, affecting the efficiency of the comprehensive index evaluation of the forest. Summary of the invention

[0004] The purpose of the present invention is to disclose a forest quality comprehensive index evaluation method and system, so as to solve the technical problem of how to improve the existing shooting scheme and obtain a more reasonable number of aerial images in the process of evaluating the comprehensive index of forest quality using aerial photography technology, so as to improve the efficiency of comprehensive index evaluation of forest quality.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for evaluating a comprehensive forest quality index, comprising:

[0007] S1, using an improved aerial photography scheme to photograph the forest to be evaluated and obtain multiple aerial images;

[0008] S2, obtain a stitched image based on multiple aerial images;

[0009] S3, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image;

[0010] S4, calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate;

[0011] Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including:

[0012] S11, obtaining a map of an area marked with forests to be evaluated;

[0013] S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map;

[0014] S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1;

[0015] S14, screening the sub-rectangles in K1 to obtain a set K2;

[0016] S15, respectively obtaining the altitude of the center of each sub-rectangle in K2;

[0017] S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system;

[0018] S17, determine the route using the following method:

[0019] S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude;

[0020] S172, the process of determining the hth route is as follows:

[0021] The first step is to obtain the interval between the h-1th route and the The straight line ;

[0022] Step 2: Get the straight line The set of sub-rectangles passed through ;

[0023] The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ;

[0024] Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5;

[0025] Step 5: Add 1 to the value of h and go to step 1;

[0026] Step 6: Obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route;

[0027] S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

[0028] Preferably, based on Calculate the interval between the hth route and the h-1th route ,include:

[0029]

[0030] Representing a collection The total number of sub-rectangles in , represents the altitude of the center of sub-rectangle i; express The average altitude of the centers of the sub-rectangles in express The maximum altitude of the center of the sub-rectangle in express The number of sub-rectangles in which is extended; is the altitude weight, is the extension quantity weight.

[0031] Preferably, the process of obtaining the extension number of the sub-rectangle includes:

[0032] S10, respectively obtain , the X-axis coordinate of the center of each sub-rectangle;

[0033] S20, in the order of X-axis coordinates from small to large, Each sub-rectangle in is numbered consecutively, the minimum number is 1, and the numbers are all integers;

[0034] S30, In the calculation, the sub-rectangle with the smallest number is used as the calculation rectangle, and d is used to represent the number of the calculation rectangle. The calculation rectangle is stored in a temporary set.

[0035] S40, calculating the difference in altitude between the centers of the sub-rectangles numbered d and d+1;

[0036] S50, determining whether the difference is less than a set difference threshold, if so, proceeding to S60; if not, proceeding to S70;

[0037] S60, store the sub-rectangle numbered d+1 into a temporary set, and determine Is it an empty set? If so, go to S80; if not, add 1 to the value of d and go to S40; if not, go to S80;

[0038] S70: Remove the sub-rectangle from the temporary set. , record the total number of sub-rectangles in the temporary set, reset the temporary set to an empty set, and enter S30;

[0039] S80: Taking the maximum value of the total number of sub-rectangles in all obtained temporary sets as the extension number of the sub-rectangles.

[0040] Preferably, calculating the difference in altitude between the centers of the sub-rectangles numbered d and d+1 includes:

[0041] Use the following formula to calculate the difference in altitude between the centers of the sub-rectangles numbered d and d+1: :

[0042]

[0043] and Respectively represent the altitudes of the centers of the sub-rectangles numbered d and d+1.

[0044] Preferably, flying along the route at a preset aerial photography altitude and taking photos includes:

[0045] When the UAV flies along the route and takes pictures, the longer side of the aerial image taken is perpendicular to the direction of the route, and the shorter side is parallel to the direction of the route.

[0046] Preferably, the aerial photography equipment includes any one of a fixed-wing drone, a multi-rotor drone, a hybrid drone and a vertical take-off and landing drone.

[0047] Preferably, obtaining a stitched image based on multiple aerial images includes:

[0048] All aerial images are stitched together to obtain a stitched image.

[0049] Preferably, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image includes:

[0050] Obtaining a forest area A1 to be evaluated in the stitched image;

[0051] In area A1, obtain area A2 belonging to vegetation;

[0052] The vegetation coverage is calculated using the following formula:

[0053]

[0054] represents the vegetation coverage rate, represents the area of ​​region A1, Indicates the area of ​​region A2.

[0055] Preferably, the comprehensive evaluation index of the forest to be evaluated is calculated based on the vegetation coverage rate, including:

[0056] The comprehensive evaluation index is calculated using the following formula:

[0057]

[0058] represents the comprehensive evaluation index, Represents a set of evaluation indicators including vegetation coverage. represents the weight of evaluation index j, Represents the score of evaluation index j.

[0059] In a second aspect, the present invention provides a forest quality comprehensive index evaluation system, comprising a photographing device, a stitching device, a first calculating device, and a second calculating device;

[0060] The photographing device is used to photograph the forest to be evaluated by adopting an improved aerial photography scheme to obtain multiple aerial images;

[0061] The stitching device is used to obtain a stitched image based on multiple aerial images;

[0062] The first calculation device is used to calculate the vegetation coverage of the forest to be evaluated based on the spliced ​​image;

[0063] The second calculation device is used to calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate;

[0064] Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including:

[0065] S11, obtaining a map of an area marked with forests to be evaluated;

[0066] S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map;

[0067] S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1;

[0068] S14, screening the sub-rectangles in K1 to obtain a set K2;

[0069] S15, respectively obtaining the altitude of the center of each sub-rectangle in K2;

[0070] S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system;

[0071] S17, determine the route using the following method:

[0072] S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude;

[0073] S172, the process of determining the hth route is as follows:

[0074] The first step is to obtain the interval between the h-1th route and the The straight line ;

[0075] Step 2: Get the straight line The set of sub-rectangles passed through ;

[0076] The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ;

[0077] Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5;

[0078] Step 5: Add 1 to the value of h and go to step 1;

[0079] Step 6: Obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route;

[0080] S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

[0081] Beneficial effects:

[0082] Compared with the existing shooting methods, the routes of the present invention not only calculate the intervals between routes based on the altitude change rate, but also calculate the intervals between routes based on the extension number of sub-rectangles, so as to avoid obtaining larger intervals when the continuity of the area with a higher altitude change rate is worse in the area passed by the route, thereby avoiding setting too small intervals between routes when an area with a higher altitude change rate appears, and can effectively reduce the number of routes. In addition, the present invention uses an adaptive shooting interval to shoot on the same route, thereby increasing the number of aerial images of the area with a higher altitude change rate, and maintaining the effectiveness of the spliced ​​images obtained by splicing the aerial images obtained by shooting. Therefore, the present invention can obtain a more reasonable number of aerial images, significantly reduce the total number of aerial images obtained, and can effectively improve the efficiency of comprehensive index evaluation of forest quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0084] Figure 1 It is a schematic diagram of a forest quality comprehensive index evaluation method of the present invention.

[0085] Figure 2 It is a schematic diagram of the route of the present invention. DETAILED DESCRIPTION

[0086] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0087] like Figure 1As shown, the present invention provides a forest quality comprehensive index evaluation method, comprising:

[0088] S1, using an improved aerial photography scheme to photograph the forest to be evaluated and obtain multiple aerial images;

[0089] S2, obtain a stitched image based on multiple aerial images;

[0090] S3, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image;

[0091] S4, calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate;

[0092] Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including:

[0093] S11, obtaining a map of an area marked with forests to be evaluated;

[0094] S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map;

[0095] S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1;

[0096] S14, screening the sub-rectangles in K1 to obtain a set K2;

[0097] S15, respectively obtaining the altitude of the center of each sub-rectangle in K2;

[0098] S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system;

[0099] S17, determine the route using the following method:

[0100] S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude;

[0101] S172, the process of determining the hth route is as follows:

[0102] The first step is to obtain the interval between the h-1th route and the The straight line ;

[0103] Step 2: Get the straight line The set of sub-rectangles passed through ;

[0104] The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ;

[0105] Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5;

[0106] Step 5: Add 1 to the value of h and go to step 1;

[0107] The sixth step is to obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route; the routes obtained are as follows: Figure 2 As shown by the dotted lines in the figure; all adjacent dotted lines are parallel to each other; the outermost one is the minimum circumscribed rectangle, and the irregular shape is the area of ​​the forest to be evaluated;

[0108] S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

[0109] In the process of acquiring aerial images, the present invention does not calculate the height between flight routes based on each pixel point in the forest area to be evaluated, because this will result in an excessive number of pixels that need to be calculated. Instead, the distance between flight routes is calculated by replacing the height of all pixel points in the sub-rectangle with the altitude of the center, so that the Y-axis coordinates and Y-axis coordinates of all flight routes can be obtained more efficiently.

[0110] In addition, in the process of route planning of the present invention, the route is perpendicular to the direction of the shorter side. This acquisition method can not only reduce the number of routes, but also reduce the number of turns of the aerial photography equipment, effectively shortening the total flight distance of the aerial photography equipment, which is conducive to improving the efficiency of aerial photography.

[0111] Specifically, the longer side of the minimum circumscribed rectangle refers to the side in the length direction, and the shorter side refers to the side in the width direction. For example, if the length of the minimum circumscribed rectangle is 500 meters and the width is 100 meters, the longer side is any one of the two sides of 500 meters; the shorter side is any one of the two sides of 100 meters.

[0112] Specifically, the length of the aerial image corresponding to the length in real space can be obtained as follows:

[0113] Get the length Z corresponding to one pixel point in the aerial image in real space;

[0114] If the length of the aerial image is Len, then the length of the aerial image in real space is Z. Len.

[0115] Preferably, the minimum bounding rectangle is divided into a plurality of sub-rectangles of the same area, including:

[0116] Calculate the length suL and width suW of the sub-rectangle as follows;

[0117]

[0118]

[0119] and They represent the length and width of the minimum circumscribed rectangle respectively; ns represents the area control coefficient;

[0120] Divide the minimum enclosing rectangle into ns ns sub-rectangles of the same area.

[0121] Preferably, the process of obtaining the area control coefficient includes:

[0122] S21, initialize the value of ns to 2;

[0123] S22, divide the minimum enclosing rectangle into ns ns sub-rectangles with the same area, save all the obtained sub-rectangles into a collection ;

[0124] S23, calculation The image information gap coefficient of the sub-rectangle in ;

[0125] S24, divide the minimum enclosing rectangle into (ns+1) (ns+1) sub-rectangles with the same area, save all the obtained sub-rectangles into a collection ;

[0126] S25, calculation The image information gap coefficient of the sub-rectangle in ;

[0127] S26, Judgment | - | Is it less than the set information gap coefficient threshold? If so, go to S27; if not, go to S28;

[0128] S27, taking the value of ns obtained by the most recent update as the area control coefficient;

[0129] S28, determining whether the accumulated different number of values ​​is greater than a preset number threshold, if not, proceeding to S29; if yes, proceeding to S30;

[0130] S29, calculate the adaptive change , add the value of ns to After that, the updated ns value is obtained and the process goes to S22;

[0131] S30, obtaining the minimum value of all obtained information gap coefficients, and taking the value of ns corresponding to the minimum value of the information gap coefficient as the area control coefficient.

[0132] The area control coefficient of the present invention is not a fixed value, because the altitude changes are different for different forests to be evaluated. Therefore, if a fixed value of the area control coefficient is set, the area of ​​the sub-rectangle is likely to be too large or too small. If the area of ​​the sub-rectangle is too large, the center of the sub-rectangle cannot effectively represent the altitude of the sub-rectangle, resulting in a large error in the route calculated later. If the area of ​​the sub-rectangle is too small, the number of altitudes required to be calculated when calculating the intervals between routes cannot be significantly reduced in subsequent calculations, and the goal of more efficiently obtaining the Y-axis coordinates and Y-axis coordinates of all routes cannot be achieved.

[0133] Therefore, the present invention calculates the information gap coefficients of the sub-rectangles obtained by the area control coefficients of two different values, so as to determine whether the information gap coefficients between the sub-rectangles obtained by the two area control coefficients meet the set iteration end conditions, and then obtains the area control coefficient that makes the gap in the information contained between different sub-rectangles as small as possible, so that the altitude of the center of the sub-rectangle can more effectively represent the overall altitude of the sub-rectangle.

[0134] Preferably, if the sub-rectangle is completely outside the area of ​​the forest to be evaluated, the image information gap coefficient of the sub-rectangle is 0.

[0135] Preferably, the information gap coefficient The calculation formula is:

[0136]

[0137] Representing a collection The one-dimensional image entropy of sub-rectangle k in; express The average value of the one-dimensional image entropy of the sub-rectangles in , express The maximum value of the one-dimensional image entropy of the sub-rectangle in .

[0138] The information gap coefficient of the present invention is calculated based on the one-dimensional image entropy. When the difference in the one-dimensional image entropy between the sub-rectangles is smaller, the information gap between different sub-rectangles is smaller, and at this time, the information gap coefficient is smaller; when the difference in the one-dimensional image entropy between the sub-rectangles is larger, the information gap between different sub-rectangles is larger, and at this time, the information gap coefficient is larger.

[0139] Therefore, through the information gap coefficient, the present invention can achieve effective acquisition of the area control coefficient.

[0140] The calculation method of is calculated in the same way.

[0141] Preferably, the information gap coefficient threshold is set to 2.

[0142] Preferably, the preset quantity threshold is 100.

[0143] Preferably, the adaptive change The calculation process includes:

[0144] like Greater than or equal to 0, then

[0145] ;

[0146] like Less than 0, then

[0147] ;

[0148] Indicates that the minimum enclosing rectangle is divided into (ns-1) After (ns-1) sub-rectangles of the same area, the information gap coefficient is calculated; Indicates the reference value of the adaptive change amount, Indicates the change value of the adaptive change amount.

[0149] In the present invention, the variation of the area control coefficient is not a fixed value, because this easily leads to too many iterations, affecting the efficiency of determining the area control coefficient. Therefore, when the difference between the information gap coefficients is in a trend of expansion, the present invention controls the adaptive variation to expand accordingly, so that the optimal area control coefficient can be approached faster; when the difference between the information gap coefficients is in a trend of reduction, the present invention controls the adaptive variation to reduce accordingly, so that the optimal area control coefficient can be approached by a smaller variation, reducing the gap between the final area control coefficient and the optimal area control coefficient, and obtaining a more accurate area control coefficient. Moreover, the change of the adaptive variation of the present invention can change with the change of the difference between the information gap coefficients, so that the variation can be more adapted to the change of the actual image information gap coefficient.

[0150] Preferably, the reference value of the adaptive change amount is 4, and the change value of the adaptive change amount is 2.

[0151] Preferably, the sub-rectangles in K1 are screened to obtain a set K2, including:

[0152] The sub-rectangles that are completely outside the area of ​​the forest to be evaluated are deleted from the set K1 to obtain a set K2.

[0153] Screening can avoid introducing too many areas that do not belong to the forest to be evaluated into the route planning process.

[0154] Preferably, based on Calculate the interval between the hth route and the h-1th route ,include:

[0155]

[0156] Representing a collection The total number of sub-rectangles in , represents the altitude of the center of sub-rectangle i; express The average altitude of the centers of the sub-rectangles in express The maximum altitude of the center of the sub-rectangle in express The number of sub-rectangles in which is extended; is the altitude weight, is the extension quantity weight.

[0157] In the present invention, the interval between two adjacent routes can change with the fluctuation degree of the altitude in the area through which the route passes and the change of the extension number of the sub-rectangle. The larger the fluctuation range of the altitude and the smaller the extension number of the sub-rectangle, the larger the interval. Thus, it is possible to avoid only considering the fluctuation range of the altitude on the route, that is, the altitude change rate to calculate the interval between the routes. Because if in a route, most of the areas are very close in altitude, while the altitude of a small part of the area is much higher than the rest, this will cause the calculated altitude to fluctuate greatly. If only this factor is considered, the interval between the calculated routes will be too small, resulting in too many aerial images being taken of areas with similar altitudes.

[0158] Therefore, the present invention also adds a parameter called extension number, which represents the maximum length of areas with similar altitudes on the route. When the fluctuation amplitude of the altitude remains unchanged, the larger the extension number, the greater the proportion of areas with similar altitudes on the route. At this time, the intervals between the routes are larger, thereby effectively reducing the probability of the obtained route intervals being too small.

[0159] Preferably, the altitude weight is , the extension quantity weight is .

[0160] Preferably, the process of obtaining the extension number of the sub-rectangle includes:

[0161] S10, respectively obtain , the X-axis coordinate of the center of each sub-rectangle;

[0162] S20, in the order of X-axis coordinates from small to large, Each sub-rectangle in is numbered consecutively, the minimum number is 1, and the numbers are all integers;

[0163] S30, In the calculation, the sub-rectangle with the smallest number is used as the calculation rectangle, and d is used to represent the number of the calculation rectangle. The calculation rectangle is stored in a temporary set.

[0164] S40, calculating the difference in altitude between the centers of the sub-rectangles numbered d and d+1;

[0165] S50, determining whether the difference is less than a set difference threshold, if so, proceeding to S60; if not, proceeding to S70;

[0166] S60, store the sub-rectangle numbered d+1 into a temporary set, and determine Is it an empty set? If so, go to S80; if not, add 1 to the value of d and go to S40; if not, go to S80;

[0167] S70: Remove the sub-rectangle from the temporary set. , record the total number of sub-rectangles in the temporary set, reset the temporary set to an empty set, and enter S30;

[0168] S80: Taking the maximum value of the total number of sub-rectangles in all obtained temporary sets as the extension number of the sub-rectangles.

[0169] The extension number represents the maximum number of sub-rectangles whose altitude differences in the continuous sub-rectangles are within the set requirements. The sub-rectangle is obtained as the calculation rectangle, the extension number starting from different calculation rectangles is obtained, and finally the maximum value of the total number of sub-rectangles in the temporary set is used as the extension number of the sub-rectangle, thereby obtaining the extension number that can represent the length of the area with similar altitude on the route.

[0170] Preferably, the difference threshold is set to , for The maximum altitude of the center of the sub-rectangle in .

[0171] Preferably, calculating the difference in altitude between the centers of the sub-rectangles numbered d and d+1 includes:

[0172] Use the following formula to calculate the difference in altitude between the centers of the sub-rectangles numbered d and d+1: :

[0173]

[0174] and Respectively represent the altitudes of the centers of the sub-rectangles numbered d and d+1.

[0175] Preferably, flying along the route at a preset aerial photography altitude and taking photos includes:

[0176] When the UAV flies along the route and takes pictures, the longer side of the aerial image taken is perpendicular to the direction of the route, and the shorter side is parallel to the direction of the route.

[0177] In another embodiment, the shorter side of the aerial image is perpendicular to the direction of the flight path, and the longer side is parallel to the direction of the flight path.

[0178] Preferably, the aerial photography equipment includes any one of a fixed-wing drone, a multi-rotor drone, a hybrid drone and a vertical take-off and landing drone.

[0179] When the aerial photography equipment is shooting, the position of entering the route is at one end of the route, and the position of leaving the route is at the other end of the route. After the two adjacent routes are connected end to end, a complete aerial photography path is obtained.

[0180] Preferably, obtaining a stitched image based on multiple aerial images includes:

[0181] All aerial images are stitched together to obtain a stitched image.

[0182] Since it is ensured that there is an overlapping area between two aerial images with adjacent shooting coordinates during aerial photography, new aerial images can be continuously added to the already stitched images, and finally all aerial images can be stitched together.

[0183] Preferably, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image includes:

[0184] Obtaining a forest area A1 to be evaluated in the stitched image;

[0185] In area A1, obtain area A2 belonging to vegetation;

[0186] The vegetation coverage is calculated using the following formula:

[0187]

[0188] represents the vegetation coverage rate, represents the area of ​​region A1, Indicates the area of ​​region A2.

[0189] Preferably, the comprehensive evaluation index of the forest to be evaluated is calculated based on the vegetation coverage rate, including:

[0190] The comprehensive evaluation index is calculated using the following formula:

[0191]

[0192] represents the comprehensive evaluation index, Represents a set of evaluation indicators including vegetation coverage. represents the weight of evaluation index j, Represents the score of evaluation index j.

[0193] Preferably, It also includes species diversity, economic value, etc.

[0194] When scoring, the richer the species, the higher the score, and the higher the economic value, the higher the score. The weights of different evaluation indicators can also be set according to actual conditions. For example, when When only vegetation coverage, species diversity, and economic value are included, the weight of species diversity is , the weight of economic value is , the weight of vegetation coverage is .

[0195] Preferably, the adaptive shooting interval is calculated using the following formula:

[0196]

[0197] represents the distance between the u-th aerial image and the u+1-th aerial image on the route, It indicates the length in real space corresponding to the width of an aerial image captured by an aerial photography device flying along a route at a preset aerial photography altitude; represents the standard deviation of the image gradient of the pixels in the u-th aerial image that do not belong to the u-1-th aerial image. Represents the median value of the image gradient of the pixel points in the area that does not belong to the u-1th aerial image in the u-th aerial image.

[0198] During the process of shooting on the same route, there are overlapping areas between two adjacent aerial images. Therefore, the present invention calculates the adaptive shooting interval by using the area outside the area overlapped with the previous aerial image in the latter aerial image, so that when the fluctuation of the image gradient of the pixel point is greater, a smaller shooting interval can be set, so that more aerial images can be taken for the area with greater fluctuation of the image gradient, that is, the area with greater altitude change rate. In this way, it can cooperate with the method of determining the distance between routes of the present invention. When only a small section passes through an area with a large altitude change rate in the route, a larger distance between routes is still set, and then more aerial images of different angles are obtained for these areas with a large altitude change rate through the adaptive shooting interval between aerial images in the route, effectively reducing the area of ​​the area that cannot be photographed due to occlusion, thereby improving the accuracy of the vegetation coverage calculated based on the aerial images.

[0199] Preferably, the value of u is greater than or equal to 2. The first aerial image is taken at the starting point of the route, and the shooting interval between the second aerial image and the first aerial image is .

[0200] The present invention also provides a forest quality comprehensive index evaluation system, comprising a shooting device, a splicing device, a first calculation device and a second calculation device;

[0201] The photographing device is used to photograph the forest to be evaluated by adopting an improved aerial photography scheme to obtain multiple aerial images;

[0202] The stitching device is used to obtain a stitched image based on multiple aerial images;

[0203] The first calculation device is used to calculate the vegetation coverage of the forest to be evaluated based on the spliced ​​image;

[0204] The second calculation device is used to calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate;

[0205] Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including:

[0206] S11, obtaining a map of an area marked with forests to be evaluated;

[0207] S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map;

[0208] S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1;

[0209] S14, screening the sub-rectangles in K1 to obtain a set K2;

[0210] S15, respectively obtaining the altitude of the center of each sub-rectangle in K2;

[0211] S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system;

[0212] S17, determine the route using the following method:

[0213] S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude;

[0214] S172, the process of determining the hth route is as follows:

[0215] The first step is to obtain the interval between the h-1th route and the The straight line ;

[0216] Step 2: Get the straight line The set of sub-rectangles passed through ;

[0217] The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ;

[0218] Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5;

[0219] Step 5: Add 1 to the value of h and go to step 1;

[0220] Step 6: Obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route;

[0221] S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

[0222] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A forest quality comprehensive index evaluation method, characterized in that: include: S1, using an improved aerial photography scheme to photograph the forest to be evaluated and obtain multiple aerial images; S2, obtain a stitched image based on multiple aerial images; S3, calculating the vegetation coverage of the forest to be evaluated based on the spliced ​​image; S4, calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate; Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including: S11, obtaining a map of an area marked with forests to be evaluated; S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map; S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1; S14, screening the sub-rectangles in K1 to obtain a set K2; S15, respectively obtaining the altitude of the center of each sub-rectangle in K2; S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system; S17, determine the route using the following method: S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude; S172, the process of determining the hth route is as follows: The first step is to obtain the interval between the h-1th route and the The straight line ; Step 2: Get the straight line The set of sub-rectangles passed through ; The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ; Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5; Step 5: Add 1 to the value of h and go to step 1; Step 6: Obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route; S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

2. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: based on Calculate the interval between the hth route and the h-1th route ,include: ； Representing a collection The total number of sub-rectangles in , represents the altitude of the center of sub-rectangle i; express The average altitude of the centers of the sub-rectangles in express The maximum altitude of the center of the sub-rectangle in express The number of sub-rectangles in which is extended; is the altitude weight, is the extension quantity weight.

3. A forest quality comprehensive index evaluation method according to claim 2, characterized in that: The process of obtaining the extension number of the sub-rectangle includes: S10, respectively obtain , the X-axis coordinate of the center of each sub-rectangle; S20, in the order of X-axis coordinates from small to large, Each sub-rectangle in is numbered consecutively, the minimum number is 1, and the numbers are all integers; S30, In the calculation, the sub-rectangle with the smallest number is used as the calculation rectangle, and d is used to represent the number of the calculation rectangle. The calculation rectangle is stored in a temporary set. S40, calculating the difference in altitude between the centers of the sub-rectangles numbered d and d+1; S50, determining whether the difference is less than a set difference threshold, if so, proceeding to S60; if not, proceeding to S70; S60, store the sub-rectangle numbered d+1 into a temporary set, and determine Is it an empty set? If so, go to S80; if not, add 1 to the value of d and go to S40; if not, go to S80; S70: Remove the sub-rectangle from the temporary set. , record the total number of sub-rectangles in the temporary set, reset the temporary set to an empty set, and enter S30; S80: Taking the maximum value of the total number of sub-rectangles in all obtained temporary sets as the extension number of the sub-rectangles.

4. A forest quality comprehensive index evaluation method according to claim 3, characterized in that: Calculate the difference in altitude between the centers of sub-rectangles numbered d and d+1, including: Use the following formula to calculate the difference in altitude between the centers of the sub-rectangles numbered d and d+1: : ； and Respectively represent the altitudes of the centers of the sub-rectangles numbered d and d+1.

5. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: Fly along the route at a preset aerial photography altitude and take photos, including: When the UAV flies along the route and takes pictures, the longer side of the aerial image taken is perpendicular to the direction of the route, and the shorter side is parallel to the direction of the route.

6. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: Aerial photography equipment includes any of fixed-wing drones, multi-rotor drones, hybrid drones, and vertical take-off and landing drones.

7. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: Get a stitched image based on multiple aerial images, including: All aerial images are stitched together to obtain a stitched image.

8. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: Calculate the vegetation coverage of the forest to be evaluated based on the mosaic image, including: Obtaining a forest area A1 to be evaluated in the stitched image; In area A1, obtain area A2 belonging to vegetation; The vegetation coverage is calculated using the following formula: ； represents the vegetation coverage rate, represents the area of ​​region A1, Indicates the area of ​​region A2.

9. A forest quality comprehensive index evaluation method according to claim 1, characterized in that: The comprehensive evaluation index of the forest to be evaluated is calculated based on the vegetation coverage rate, including: The comprehensive evaluation index is calculated using the following formula: ； represents the comprehensive evaluation index, Represents a set of evaluation indicators including vegetation coverage. represents the weight of evaluation index j, Represents the score of evaluation index j.

10. A forest quality comprehensive index evaluation system, characterized in that: It includes a shooting device, a stitching device, a first calculating device and a second calculating device; The photographing device is used to photograph the forest to be evaluated by adopting an improved aerial photography scheme to obtain multiple aerial images; The stitching device is used to obtain a stitched image based on multiple aerial images; The first calculation device is used to calculate the vegetation coverage of the forest to be evaluated based on the spliced ​​image; The second calculation device is used to calculate the comprehensive evaluation index of the forest to be evaluated based on the vegetation coverage rate; Among them, an improved aerial photography scheme was used to photograph the forest to be evaluated, and multiple aerial images were obtained, including: S11, obtaining a map of an area marked with forests to be evaluated; S12, obtaining the minimum circumscribed rectangle of the forest area to be evaluated in the map; S13, dividing the minimum circumscribed rectangle into multiple sub-rectangles of the same area, and saving all the sub-rectangles into a set K1; S14, screening the sub-rectangles in K1 to obtain a set K2; S15, respectively obtaining the altitude of the center of each sub-rectangle in K2; S16, establishing a rectangular coordinate system with the longer side of the minimum circumscribed rectangle as the X-axis and the shorter side of the minimum circumscribed rectangle perpendicular to the X-axis as the Y-axis, so that the rest of the minimum circumscribed rectangle, except for the two sides serving as the X-axis and the Y-axis, is located in the first quadrant of the rectangular coordinate system; S17, determine the route using the following method: S171, the Y-axis coordinate of the first route is , len represents the length of the aerial image in real space corresponding to the length of the aerial image obtained by the aerial photography equipment flying along the route at a preset aerial photography altitude; S172, the process of determining the hth route is as follows: The first step is to obtain the interval between the h-1th route and the The straight line ; Step 2: Get the straight line The set of sub-rectangles passed through ; The third step is based on Calculate the interval between the hth route and the h-1th route , then the Y-axis coordinate of the h-th route is ; Step 4: Judgement Is it greater than the length Ls of the shorter side of the minimum circumscribed rectangle in the rectangular coordinate system? If so, modify the Y-axis coordinate of the hth route to Ls and proceed to step 6; if not, proceed to step 5; Step 5: Add 1 to the value of h and go to step 1; Step 6: Obtain the intersection points of each route and the forest area to be evaluated, and use the minimum and maximum values ​​of the X-axis coordinates of all the intersection points as the minimum and maximum values ​​of the X-axis coordinates of the route, thereby determining the X-axis coordinate range of each route; S18, photographing the forest to be evaluated at a preset aerial photography height with an adaptive shooting interval on each route to obtain a plurality of aerial images.

Images